Early HIV treatment can save lives as well as have profound prevention benefits. But those infected with the virus first must be identified before they can be helped.

In a new study, two Northwestern University researchers report that current Centers for Disease Control and Prevention (CDC) HIV screening guidelines are too conservative and that more frequent testing would be cost-effective in the long run for both high- and low-risk groups.

The Northwestern team performed a mathematical modeling study to assess “optimal testing frequencies” for HIV screening in different risk groups. They concluded screening should be done up to every three months for the highest-risk individuals and low-risk groups should be tested every three years.

The CDC currently recommends annual testing for high-risk groups, such as people with HIV-positive sexual partners, people with multiple sexual partners, injection drug users and sex workers, and once-in-a-lifetime testing for low-risk groups (whose annual risk of acquiring HIV is only one-hundredth of one percent).

“Our results should encourage policymakers and medical professionals to reconsider how often adolescents and adults should be tested for HIV,” said Benjamin Armbruster, an assistant professor of industrial engineering and management sciences at Northwestern’s McCormick School of Engineering and Applied Science.

He and Aaron Lucas, a doctoral student in Armbruster’s group, modeled various scenarios in an attempt to “optimize the tradeoff” between the societal costs of testing versus the benefits of earlier HIV diagnosis over a patient’s lifetime.

Their study is published in the March 2013 issue of AIDS, the official journal of the International AIDS Society.

Frequent testing has been shown to be an effective method for identifying new HIV infections. In the past, people with new HIV infections weren’t treated until they had significant declines in immune functioning, as measured by the CD4 cell count. But there is a growing consensus that antiretroviral treatment is beneficial for all HIV-infected patients, regardless of CD4 count. Starting treatment immediately after diagnosis also reduces the risk of transmitting HIV.

Within its limitations, the Northwestern study suggests that current recommendations for HIV testing are “too conservative, especially for low-risk groups who would benefit from more frequent testing.”